toupper, tolower - convert letter to upper or lower case
SYNOPSIS
#include <ctype.h>
int toupper (int c);
int tolower (int c);
DESCRIPTION
toupper() converts the letter c to upper case, if possi
ble.
tolower() converts the letter c to lower case, if possi
ble.
If c is not an unsigned char value, or EOF, the behaviour
of these functions is undefined.
RETURN VALUE
The value returned is that of the converted letter, or c
if the conversion was not possible.
CONFORMING TO
ANSI C, BSD 4.3
BUGS
The details of what constitutes an uppercase or lowercase
letter depend on the current locale. For example, the
default "C" locale does not know about umlauts, so no con
version is done for them.
In some non - English locales, there are lowercase letters
with no corresponding uppercase equivalent; the German
sharp s is one example.
SEE ALSO
isalpha(3), setlocale(3), locale(7)
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